title: Molecular comparison of soluble intercellular adhesion molecule (sICAM)-1 and sICAM-3 binding to lymphocyte function-associated antigen-1.
abstract: The interactions of intercellular adhesion molecules-1 and -3 (ICAM-1 and ICAM-3) with lymphocyte function-associated antigen-1 (LFA-1) have been characterized and compared on the molecular and cellular level. Enzyme-linked immunosorbent-based molecular assays have been utilized to calculate the binding affinities of soluble ICAM-1 (sICAM-1) and soluble ICAM-3 (sICAM-3) for LFA-1. Consistent with previously published data, we found that sICAM-1 binds to LFA-1 with an affinity of approximately 60 nM. In contrast, sICAM-3 binds to LFA-1 with an affinity approximately 9 times weaker ( approximately 550 nM). Both sICAM-1 and sICAM-3 require divalent cations for binding. Specifically, both Mg2+ and Mn2+ support high affinity adhesion, although interestingly, high concentrations of Ca2+ decrease the affinity of each molecule for LFA-1 substantially. Furthermore, a panel of anti-LFA-1 monoclonal antibodies were characterized for their ability to block sICAM-1 and sICAM-3/LFA-1 interactions in molecular and cellular assays to help distinguish binding sites on LFA-1 for both molecules. Finally, molecular and cellular competition experiments demonstrate that sICAM-1 and sICAM-3 compete with each other for binding to LFA-1. The above data demonstrate that sICAM-1 and sICAM-3 share a common binding site or an overlapping binding site on LFA-1 and that the apparent differences in binding sites can be attributed to different affinities of sICAM-1 and sICAM-3 for LFA-1.
authors.affiliation: Cell Adhesion Group, Department of Immunological Diseases, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877, USA. jwoska@bi-pharm.com
authors.forename: J R
authors.initials: JR
authors.lastname: Woska
authors.forename: M M
authors.initials: MM
authors.lastname: Morelock
authors.forename: D D
authors.initials: DD
authors.lastname: Jeanfavre
authors.forename: G O
authors.initials: GO
authors.lastname: Caviness
authors.forename: B J
authors.initials: BJ
authors.lastname: Bormann
authors.forename: R
authors.initials: R
authors.lastname: Rothlein
mesh_terms: D015703:Antigens, CD; D000943:Antigens, Differentiation; D001667:Binding, Competitive; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008345:Manganese / Q000378:metabolism; D016296:Mutagenesis; D014407:Tumor Cells, Cultured
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D015815:Cell Adhesion Molecules; C483616:ICAM3 protein, human; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1; D008345:Manganese; D008274:Magnesium